1. Field of the Invention
The present invention relates generally to methods for forming thin film transistor (TFT) structures which may be employed within liquid crystal display (LCD) fabrications. More particularly, the present invention relates to planarizing methods for forming thin film transistor (TFT) structures which may be employed within liquid crystal display (LCD) fabrications.
2. Description of the Related Art
Liquid crystal display (LCD) fabrications are employed as user interface devices within various types of information technology products, such as, but are not limited to, personal computer products, portable computer products and computer terminal products.
Common in the fabrication of liquid crystal display (LCD) fabrications is the use of a series of thin film transistor (TFT) structures which serves as a series of switching elements which in turn activates a series of pixel electrodes which in turn provides for operation of the liquid crystal display (LCD) fabrication.
While thin film transistor (TFT) structures are thus common and often essential in the art of liquid crystal display (LCD) fabrication, thin film transistor (TFT) structures are nonetheless not entirely without problems within the art of liquid crystal display (LCD) fabrication. In that regard, it is common in the art of thin film transistor (TFT) structure fabrication, and for purposes of providing liquid crystal displays (LCD) fabrications with enhanced performance, to employ when fabricating thin film transistor (TFT) structures within liquid crystal display (LCD) fabrications various microelectronic layers of high aspect ratio such as to ultimately provide liquid crystal display (LCD) fabrications having an increased pixel aperture ratio. As is common in the art of microelectronic fabrication in general, however, microelectronic layers of high aspect ratio when formed within thin film transistor (TFT) structures employed within liquid crystal display (LCD) fabrications often provide irregular surfaces upon which it is difficult to subsequently form additional microelectronic layers which are needed to form fully functional or reliable thin film transistor (TFT) structures or liquid crystal display (LCD) fabrications.
It is thus towards the goal of forming, with enhanced functionality and reliability, thin film transistor (TFT) structures which may employ high aspect ratio microelectronic layers, which in turn provide liquid crystal display (LCD) fabrications with enhanced performance, that the present invention is directed.
Various methods and materials have been disclosed in the arts of thin film transistor (TFT) structure fabrication and liquid crystal display (LCD) fabrication fabrication for forming thin film transistor (TFT) structures and liquid crystal display (LCD) fabrications with desirable properties. For example, Lan et al., in xe2x80x9cFully Planarized xcex1-Si:H TFTs for AM-LCDs,xe2x80x9d Proceedings of AMLCD 98 Kogakuin University, Tokyo, Jul. 9-10, 1998, pp. 77-80, discloses methods and materials which may be employed for both: (1) locally planarizing a series of gate electrode structures within a series of thin film transistors (TFT) structures which may be employed within a liquid crystal display (LCD) fabrication; and (2) globally planarizing the series of thin film transistor (TFT) structures as a whole which may be employed within the liquid crystal display (LCD) fabrication. The method employs as a planarizing material for both locally planarizing the series of gate electrode structures and globally planarizing the series of thin film transistor (TFT) structures a benzocyclobutene (BCB) planarizing material.
In addition, Lim et al., in xe2x80x9cHigh Performance Amorphous Silicon Thin Film Transistor with a Planarized SiNx/BCB Double Layered Gate Insulator,xe2x80x9d Proceedings of AMLCD 98 Kogakuin University, Tokyo, Jul. 9-10, 1998, pp. 73-76, discloses a method for forming a thin film transistor (TFT) structure which may be employed within a liquid crystal display (LCD) fabrication, where the thin film transistor (TFT) structure is formed with enhanced performance of the thin film transistor (TFT) structure for use within the liquid crystal display (LCD) fabrication. The thin film transistor (TFT) structure realizes the foregoing object by employing when fabricating the thin film transistor (TFT) structure a gate dielectric layer formed as a bilayer of a first dielectric layer formed of a benzocyclobutene (BCB) material, the first dielectric layer in turn having formed thereupon a second dielectric layer formed of a silicon nitride dielectric material.
Finally, Lyu et al., in U.S. Pat. No. 6,001,539, discloses a method for forming over a thin film transistor (TFT) structure for use within a liquid crystal display (LCD) fabrication a passivation layer which simultaneously provides an enhanced planarization of the thin film transistor (TFT) structure and an enhanced adhesion of a pixel electrode layer formed upon the passivation layer. To realize the foregoing objects, the method employs the passivation layer formed at least in part of an organo-silicon planarizing material such that due to flow characteristics of the organo-silicon material the passivation layer may be formed with enhanced planarization upon a thin film transistor (TFT) structure, and such that upon oxygen plasma oxidation of the passivation layer there may be formed a silicon oxide material which provides for enhanced adhesion of a pixel electrode formed upon the oxygen plasma oxidized passivation layer.
Desirable in the art of microelectronic fabrication are additional methods and materials which may be employed for forming, with enhanced functionality and reliability, thin film transistor (TFT) structures which may employ high aspect ratio microelectronic layers, which in turn provide liquid crystal display (LCD) fabrications with enhanced performance.
It is towards the foregoing objects that the present invention is directed.
A first object of the present invention is to provide a method for forming a thin film transistor (TFT) structure which may be employed within a liquid crystal display (LCD) fabrication.
A second object of the present invention is to provide a method for forming a thin film transistor (TFT) structure in accord with the first object of the present invention, wherein the thin film transistor (TFT) structure is formed with enhanced functionality and reliability.
A third object of the present invention is to provide a method for forming a thin film transistor (TFT) structure in accord with the first object of the present invention or the second object of the present invention, which method is readily commercially implemented.
In accordance with the objects of the present invention, there is provided by the present a method for forming a thin film transistor (TFT) structure which may be employed within a liquid crystal display (LCD) fabrication.
To practice the method of the present invention, there is first provided a substrate. There is then formed over the substrate a gate electrode. There is then formed adjacent to the gate electrode but not covering a top surface of the gate electrode a backfilling dielectric layer. There is then formed over and covering the top surface of the gate electrode a gate dielectric layer. There is then formed over and covering the gate dielectric layer an active semiconductor layer. Finally, there is then formed over and in electrical communication with the active semiconductor layer a pair of source/drain electrodes, where the pair of source/drain electrodes has a separation distance which defines a channel region of the active semiconductor layer.
The method for forming the thin film transistor (TFT) structure in accord with the present invention contemplates a thin film transistor (TFT) structure formed in accord with the method for forming the thin film transistor (TFT) structure in accord with the present invention.
The present invention provides a method for forming a thin film transistor (TFT) structure which may be employed within a liquid crystal display (LCD) fabrication, wherein the thin film transistor (TFT) structure is formed with enhanced functionality and reliability. The present invention realizes the foregoing object by employing when forming the thin film transistor (TFT) structure for use within the liquid crystal display (LCD) fabrication a backfilling dielectric layer formed adjacent a gate electrode formed over a substrate, where the backfilling dielectric layer is not formed covering a top surface of the gate electrode formed over the substrate. By employing such a backfilling dielectric layer there is compensated a topographic variation of the gate electrode within the thin film transistor (TFT) structure such that the thin film transistor (TFT) structure may be formed with enhanced functionality and reliability.
The method of the present invention is readily commercially implemented. The present invention employs methods and materials as are generally known in the art of microelectronic fabrication, but employed within the context of specific process limitations and structural limitations to provide the present invention. Since it is thus a process limitation and a structural limitation which provides at least in part provides the present invention, rather than the existence of methods and materials which provides the present invention, the method of the present invention is readily commercially implemented.